Figure 1.

(A) A flow-chart showing the preparation of the muscle homogenate, the thin-filament fraction, and the soluble muscle fraction. (B) Protein compositions of preparations used in the present study shown by SDS/PAGE (7.5% polyacrylamide): muscle homogenate (lane 1); the thin-filament fraction (lane 2); and the soluble fraction (lane 3). Most twitchin was removed from the soluble fraction (lane 4) to examine its role in the catch state. To identify thick-filament components essential for the catch state, we prepared paramyosin-free thick filaments (lane 5) and purified myosin filaments (lane 6). We also purified twitchin (lane 7) and added it to the purified myosin filaments (lane 8). Lane 9 shows marker proteins with their molecular masses in kDa shown on the right.